The State of the Atmosphere: Sunday, October 26, 2014

MISSING: Winter.

Okay, not entirely. While Denver’s average first measurable snowfall came and went last week, there are still many snowy months ahead. We were spoiled with a cool(er) wet summer, so a streak of warm, calm weather only seems fair. Right? Now we’ll see if we can follow this with a more interesting winter than recent years.

We finished this past week with record warm temperatures. Denver recorded a high of 82 degrees at Denver International Airport Friday, breaking the old record of 80 degrees set in 2011 for the date. The normal high low for the this time of year is 62 and 34 -- numbers we’ve been nowhere near for some time now.

While I know a lot of the snow lovers that follow the blog were as eager as some of us for an October snow, a snowy October does not always bode well for a snowy winter. On average, Denver receives just 4.2 inches of snow during the month of October, which equates to our seventh snowiest month of the year. The next six months all average more snow than October does, with next month (November) taking the four-spot.

Of the five analog years outlined in our Winter Outlook, Part 1, only one of them had a impressive October snowfall -- 2009, which has dropped lower in the list of analogs over recent months. Additionally, all but one of these years (1976) had average or above average snowfall for the season, though many of the years the snow came during the middle to second half of the winter (or in the case of 2002-2003 virtually all at once in March).

Much cooler start to the week
We’ll finally say goodbye to our well above average temperatures to start the coming week. As discussed in last week’s State of the Atmosphere, this cold front won’t be anything to write home about -- but we’ll certainly feel the punch after temperatures running so far above average for so long. It’s also possible that we see our first below freezing temperatures of the season by early Tuesday morning.

This system will carry some moisture with it, but not a ton. For the time being we’re going with scattered showers for the eastern Plains, and a chance for snow/snow showers at higher elevations for tonight and Monday. The National Weather Service has issued a Winter Weather Advisory for the north-central mountains for 2 to 5 inches of snow possible above 9500 feet.

Here are the forecast 2 meter temperatures for yesterday afternoon (Ieft), and then Monday afternoon (right), much cooler across the west.

Model mess By the middle of the week back comes the warmth as the real cold slips into the east (sound familiar?). To be perfectly honest, there’s not a lot in the medium range that looks all that convincingly cold, snowy, or for that matter, interesting. Models have been a pretty big mess over the last few weeks in the long-range pattern and with that it’s pretty hard to get behind any one solution that they spit out. My prediction is that we get a decent cold shot before too long, and that it could sneak up on us a bit as I’m not all the impressed with medium range ensembles.

The next best chance at snow could come during the first week of November -- and even that could be a stretch, though it does look generally colder. At one point models were trying to bring in a deeper trough for the Oct 30 - Nov 2 time period, and now this looks to be more like Nov 5 to Nov 9, really a tell-tale sign they don’t have a good handle on things.

An excellent example of this is the Canadian model. The top image is the 00z run from October 24 for forecast hour 348, or November 7. Below is the 00z Canadian ensemble run on October 25 for the same forecast hour. Notice the positioning of the lower height anomalies… a few days ago across southeast Colorado on November 7, now they’re still back off the west coast for the same period! It still does progress a trough across the region, but it’s got a much different look to it and is several days later than previously forecast.

WeatherBell Analytics

The GFS and ECMWF ensembles continue to vary on bringing multiple disturbances across Colorado next week, the first by next Sunday, the second by the following weekend. Again, hard to get behind one solution or another at this point, but next week certainly has the look of being (in general) more interesting. The EURO ensemble control is at this time the coldest of the three models really bringing a blast of cold air across the state by next week.

Bottom line
Bottom line is there’s not much to watch at this time, at least for us. Weather stories for the coming week will be a cooler start to the week across Colorado before seasonal to warmer than normal temperatures return for the middle of the week. The cold will slip into the eastern United States for the Halloween weekend, and the Pacific Northwest which has been really getting hit with rain and snow will continue to be impacted over the coming week and into next weekend as energy from what is now Hurricane Ana get wrapped into the flow.

Here’s the current GFS precip + MSLP look for 12z next Saturday (hey look, rain and snow for northern California!):

GFS 6 precip | Weather5280 Models

And afternoon 2 meter temperature maximums for Sunday, November 1 (chilly in the east).

GFS 2meter max temperatures | Weather5280 Models

I’ll resist the urge to share with you CFSv2 temperature outlooks and some of the more grim ensemble model runs for now as I really do think that while models may be right on keeping us pretty quiet over the next 5 days+, overall they’re not handling things all that great. It’s best to have patience and see how things start to shake out as we head into the final days of October and the start of November. Next week could very well be colder.

For what it's worth, I still believe we have a good chance for a snowy winter, even if it's painfully slow to arrive.

Brendan Heberton

Brendan is founder of Weather5280. He is co-founder of FreshyMap, and develops software for geospatial data analysis and visualization.

Denver, Colorado
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